Magnetic resonance visible markers for magnetic resonance imaging guided brachytherapy

Abstract

Magnetic resonance (“MR”) visible markers for use in MR-guided placement of brachytherapy seeds, and for use in other MR-guided interventional procedures, are described. The MR-visible markers generally include a tube in which an absorbent thread assembly is disposed. The tube is made fluid-tight by sealing it at both ends with suitable end plugs. The absorbent thread assembly is soaked in a suitable MR-visible fluid.

The invention claimed is: 
     
       1. A magnetic resonance visible marker, comprising:
 a tube having a lumen and extending from a proximal end to a distal end along a length of the tube; 
 a proximal end plug arranged in the lumen at the proximal end of the tube to provide a fluid-tight seal at the proximal end of the tube; 
 a distal end plug arranged in the lumen at the distal end of the tube to provide a fluid-tight seal at the distal end of the tube such that a fluid-tight volume is formed in the lumen between the proximal end plug and the distal end plug; 
 an absorbent thread assembly spanning the lumen of the tube from the proximal end plug to the distal end plug, wherein the absorbent thread assembly has been soaked in and thereby absorbed a magnetic resonance visible fluid. 
 
     
     
       2. The magnetic resonance visible marker as recited in  claim 1 , wherein the absorbent thread assembly comprises a plurality of absorbent threads. 
     
     
       3. The magnetic resonance visible marker as recited in  claim 2 , wherein the plurality of absorbent threads are composed of a natural fiber material. 
     
     
       4. The magnetic resonance visible marker as recited in  claim 3 , wherein the plurality of absorbent threads are composed of cotton. 
     
     
       5. The magnetic resonance visible marker as recited in  claim 2 , wherein the plurality of absorbent threads are twisted together. 
     
     
       6. The magnetic resonance visible marker as recited in  claim 2 , wherein the absorbent thread assembly comprises three to five absorbent threads that are twisted together. 
     
     
       7. The magnetic resonance visible marker as recited in  claim 1 , wherein the magnetic resonance visible fluid is water. 
     
     
       8. The magnetic resonance visible marker as recited in  claim 1 , wherein the magnetic resonance visible fluid contains a magnetic resonance contrast agent. 
     
     
       9. The magnetic resonance visible marker as recited in  claim 8 , wherein the magnetic resonance contrast agent contains at least one of superparamagnetic iron oxide nanoparticles or gadolinium. 
     
     
       10. The magnetic resonance visible marker as recited in  claim 1 , wherein the magnetic resonance visible fluid is a solution of copper(II) sulfate and saline. 
     
     
       11. The magnetic resonance visible marker as recited in  claim 1 , wherein the proximal end plug and the distal end plug are composed of polyether ether ketone (PEEK). 
     
     
       12. The magnetic resonance visible marker as recited in  claim 1 , wherein the proximal end plug and the distal end plug are coupled to the lumen of the tube via an adhesive. 
     
     
       13. The magnetic resonance visible marker as recited in  claim 12 , wherein the adhesive is an epoxy. 
     
     
       14. The magnetic resonance visible marker as recited in  claim 13 , further comprising a second epoxy that is provided to the lumen distal to the distal end plug and to the lumen proximal to the proximal end plug. 
     
     
       15. The magnetic resonance visible marker as recited in  claim 14 , wherein the second epoxy is a low viscosity epoxy. 
     
     
       16. The magnetic resonance visible marker as recited in  claim 1 , wherein the tube is composed of a biocompatible material. 
     
     
       17. The magnetic resonance visible marker as recited in  claim 16 , wherein the tube is composed of polyimide. 
     
     
       18. A method for manufacturing a magnetic resonance visible marker for use with a brachytherapy seed applicator, the steps of the method comprising:
 submerging a tube in a magnetic resonance visible fluid; 
 soaking an absorbent thread assembly comprising a plurality of absorbent threads in the magnetic resonance visible fluid for a period of time; 
 after the period of time and while keeping the absorbent thread assembly and tube submerged in the magnetic resonance visible fluid:
 inserting a leading end of the absorbent thread assembly into a first end of the tube; 
 coupling a syringe to a second end of the tube and applying suction to the tube via the syringe so as to pull the absorbent thread assembly into the tube; 
 removing the syringe from the tube when the absorbent thread assembly reaches the second end of the tube and pulling the leading end of the absorbent thread assembly through the second end of the tube; 
 trimming the absorbent thread assembly flush with the first end and the second end of the tube; and 
 sealing the first end of the tube using a first end plug and the second end of the tube using a second end plug. 
 
 
     
     
       19. The method as recited in  claim 18 , wherein sealing the first end of the tube and the second end of the tube further comprises providing a low viscosity epoxy to the first end of the tube and to the second end of the tube. 
     
     
       20. The method as recited in  claim 18 , wherein the period of time is between four and twelve hours.